Patients may benefit from the infusion of therapeutic fluids into tissues surrounding a wound in a variety of ways. Local anesthetics may be infused directly to the wound site to help manage pain post-operatively. Antibiotics may be infused to a wound site to eliminate infections. Growth factors or oxygen rich fluids may be infused to facilitate wound healing and recovery. A variety of other active agents including but not limited to chemotherapeutics, stems cells, hemostatic agents, angiogenic, and anti-angiogenic agents may also provide patient benefit when delivered locally to tissues via infusion.
Traditional infusion devices are fabricated with a contiguous lumen that generally extends from the fluid source and along the entire length of the device to the tissues intended to receive the fluid. The lumen is typically formed as a continuous hollow element through extrusion or other processes, and ordinarily has a solid wall that contains exits or ports for fluid egress. If the device is intended to deliver a fluid over an extended distance within tissue, multiple ports or exits are formed along the axis of the device in an attempt to distribute the fluid from the lumen along the implanted length of the device.
For example, U.S. Pat. No. 3,821,956 to Gordhamer discloses a device for the dilation and treatment of a bovine teat. The device is hollow and has a spiral groove on the external surface of the device. There are exit ports that extend from the inner lumen of the device to the external groove. This device appears to be relatively inflexible.
In U.S. Pat. No. 4,159,720, a method of treating tissue with a device comprised of a wicking material that may be implanted in a wound is disclosed. This reference describes that the wicking material may be a hollow monofilament provided with lateral perforations through which the fluid will pass into the tissue. Alternatively, the wicking material is described as being a solid filament having spiral or longitudinal grooves in its external surface. This patent further describes the concept of attaching a suture needle directly to the wicking material to facilitate implantation of the device in tissue. For example, this reference discloses that the wick may be installed into position as if it were a suture, and in one embodiment, the wick may serve as a suture for holding the severed flesh together as well as a carrier or conduit for delivering fluid to the affected area.
U.S. Pat. No. 5,458,582 to Nakao describes an anesthesia delivery device comprising an elongate flexible tubular member in the form of a hollow tube made of bioabsorbable material, the tubular member having a proximal end portion with a continuous cylindrical side wall and a distal end portion provided with a plurality of apertures spaced longitudinally along the distal end portion.
Similarly, U.S. Pat. No. 6,626,885 describes an infusion catheter exhibiting a plurality of apertures located along the implantable segment, and a method of implantation with an auxiliary tissue-penetrating device, whereby the infusion catheter is introduced via the auxiliary tissue-penetrating device through skin adjacent to an incision site. It is generally accepted by the medical community that using a catheter entry site remote from the incision site reduces the risk of infection associated with the use of a catheter that is left in place over a period of time.
However, there are several problems associated with the approaches described in the prior art for the delivery of fluids transcutaneously. The first problem is associated with the formation of exit ports from the device. The creation of the ports requires the machining of the tube through processes such as drilling, punching, laser cutting or other suitable methods. Many of these processes are intrinsically difficult and costly, Additionally, these processes typically become more difficult and costly to implement as the diameter of the catheter decreases, with most traditional infusion catheters exhibiting large diameters in excess of 0.020″.
An additional problem of these tubular devices is that they are ordinarily smooth along the external surface. The smooth surface abuts the surrounding tissues and forms a lightly sealed surface surrounding the exit ports. This effect can result in an increase in the pressure differential from within the tube to overcome this sealing effect to enable fluid egress from the device.
In view of the drawbacks associated with the infusion devices described above, it is desirable to have an infusion device where the infusion passage is maintained in a continuous fashion from the point of fluid egress to the terminus of the device in the tissue, thereby enabling the egress of fluid from the device into the surrounding tissue along the full length of the implanted device.